The beautiful 28-year-old woman who died on the tracks beneath the wheels of a No. 2 train on New Year’s Day had come to Manhattan for a Phish concert the night before— and then disappeared on her fiancé.

Dana Ferrari, a medical assistant from Pennsylvania, went to Madison Square Garden with her beau, Blake Pupo, and his brother, family members said yesterday.

But Pupo went to the restroom during the concert, and when he returned, Dana — who died nearby at the 34th Street station — was nowhere to be found, her sister, Leslie Ferrari, 22, of Andover, NJ, told The Post.

“He’s a mess,” Leslie, who worked alongside her sister in a pediatrician’s office in Andover, said of the heartbroken Pupo.

The two were supposed to spend the night at the Marriott, Leslie said

Then she added, “We’d like to have more answers. How did she get into the train station?”

“Dana definitely wasn’t a drinker,” she added.

She recalled her sister’s last words to her — written at the stroke of midnight — as “happy new year! i love you.”

Dana was struck by a northbound train at 5:20 a.m. Tuesday.

Witnesses said she’d appeared intoxicated, staggering around before walking down some service stairs at the end of the platform — and into the mouth of the subway tunnel.

She was lying on the track bed, and by the time the motorman had spotted her, it was too late to do anything, a law-enforcement source said.

She had no identification on her, only a set of keys with a CVS card registered to Pupo, which is what investigators used to initially identify her.

Leslie said there had been no indication that anything was bothering her sister or that there was any reason for her to take her own life.

Dana grew up in Newton, NJ, and had been engaged to Pupo since 2009, according to her Facebook page.

The couple lived in Dingmans Ferry, Pa., with their dog, and often went to concerts, with his Facebook page documenting many such events, including others featuring Phish.

In Pupo’s profile photo, Dana can be seen in the background, hands in the air, holding a drink.

Leslie said the medical examiner told the family that the death appeared to be accidental and that Dana had fallen.

“It was a freak accident,” Leslie said. “She fell onto the tracks.”

But Ellen Borakove, a spokeswoman for the city Medical Examiner’s Office, said the cause of death was still listed as “pending further study.”

“We are doing testing and further investigation,” including toxicology tests, she said.